1. Field of the Invention
The present invention generally relates to a jaw folding device of jaw-type folder. More particularly, the present invention relates to a jaw folding mechanism of a jaw cylinder of a jaw folding device for jaw folding papers to be printed to form a folded print.
2. Description of the Prior Art
A conventional jaw folding mechanism for a jaw cylinder of a jaw folding device has been shown in Japanese Patent Application Open Publication No. Sho. 57-90359, Japanese Patent Application for Utility Model Open Publication No. Sho. 58-153042 and Japanese Patent for Utility Model Publication No. Sho. 59-5010.
For instance, the above publications No. Sho. 57-90359 and No. Sho. 59-5010 have provided one example of jaw folding as shown in FIG. 5 and FIG. 6. In the drawings, the jaw folding device comprises cylinder 300, a controlled jaw plate shaft 301 rotatably arranged within the groove formed in the cylinder 300 and protruding out both sides of the cylinder 300, arms 302 and, 302' fixed on the respective ends of the shaft 301, and a controlled jaw plate 303 fixed in the groove. Further, a fixed jaw plate 304 is formed on the edge of the groove of the cylinder 300 so as to face the controlled jaw plate 303. A guide rod 307 provided with a spring 305 is secured to one end of the arm 302 so as to urge the controlled jaw plate 303 toward the fixed jaw plate 304 through the urging force of the spring 305. The other end of the arm 302 is connected to a cam follower 308 which follows along the external surface of a cam 309 fixed on a machine base 310. The controlled jaw plate shaft 301 is angularly changed in accordance with the following motion of this cam follower 308 and, thus, the controlled jaw plate 303 can be isolated from the fixed jaw plate 304.
The above described conventional art No. Sho. 58-153042 provides another example of a jaw folding device, as shown in FIG. 7 and FIG. 8. In the drawings, the jaw folding device comprises a cylinder 400, a controlled jaw plate shaft 401 pivotably arranged in a groove of the cylinder 400 in such manner that at least one end of the shaft 401 protrudes from the side surface of the cylinder 400, an arm 402 fixed on the one end of the shaft 401, a controlled jaw plate 403 fixed to the shaft 401 within the groove, and an arm 411 for receiving a spring 405. A fixed jaw plate 404 is arranged at the edge of the groove formed in the cylinder 400 so as to face to the controlled jaw plate 403. In the bottom of the groove in the cylinder 400 a pair of recesses is coaxially formed with the arm 411 to receive the spring 405. A guide rod 407 is inserted in the coil 405 and its bottom end is fixed at each the recess, so as to press the controlled jaw plate 403 to the fixed jaw plate 404. The top end of the guide rod 407 is slidably inserted into an opening formed in the arm 411, so that the lower surface of the arm 411 is subjected to the urging force caused by the spring 405. Further, the arm 402 is provided with a cam follower 408 which follows along the external surface of a cam 409. According to the motion of this cam 409 the controlled jaw plate shaft 401 is angularly changed to allow the controlled jaw plate 403 to be isolate from the fixed jaw plate 404.
However, such conventional structure may cause various problems. That is the jaw folding force for holding a paper between the controlled jaw plate and the fixed jaw plate is supplied by the urging means such as the spring and the guide rod; this jaw folding force is one of the most important factors for this jaw folding device. This urging means is fixedly arranged in the cylinder so that such means will be installed in an extermely narrow space when the cylinder is assembled within a folding apparatus. This requires complicated operation and long times for the maintenance, checking, adjustment, and replacement of the jaw folding device. Further this structure limits working position for such activities, so that the operators may be endangered.